1. Technical Field
The present invention—involving adhesive applicators that apply adhesive to a lateral-edge surface of sheet bundles having been collated into sheaves, and then bind the sheaves together with cover sheets or similar coverings—relates to improvements in refilling mechanisms that supply hot-melt adhesive to a glue container, in bookbinding apparatuses or like machines that collate into sheaves sheets on which images have been formed for example in a printing or other image-forming apparatus, and apply hot-melt adhesive to a sheaf and bind it together with a cover sheet.
2. Description of the Related Art
Widely known among adhesive applicators of this type are in general those that with an applicator roll or similar device apply to an endface of a sheet sheaf adhesive in liquid form, charged into a container; the adhesives employed in such implementations are hot-melts—adhesives solid at ordinary temperatures, the solid form of which is heated and melted within a container. Advantages to the adhesives are thus that because they are in solid form at room temperature they are suited to handling and storage, and replenishing apparatus-internal containers with the adhesives is facilitated. On the other hand, included in the adhesives generally used are tackifiers and like additives—the main component of which is synthetic rubber—for increasing the adhesives' viscosity, wherein a known problem with these adhesives is that on account of their being heated to and melted at a predetermined temperature (ordinarily 130° C. to 150° C.), in melting the adhesives additive components evaporate and stick to the apparatus interior. At the same time, the fact that the adhesives solidify at ordinary temperatures requires that hardened adhesive be melted and liquefied in a short time frame at apparatus start-up.
In order to liquefy/melt the adhesive in a shorter time frame, to date, attempts whereby the glue container is scaled down and adhesive is applied by reciprocating the container along the sheet endface have been disclosed—for example in Japanese Unexamined Pat. App. Pub. No. 2004-216769. This publication presents an apparatus in which a glue container with a built-in application roller is disposed free to reciprocate along a guide rail, wherein in reciprocating the container between leftmost and rightmost positions, adhesive is applied with the application roller to an endface of a sheet sheaf. Therein, a structure is disclosed in which a high-frequency heating device disposed at the leftmost position of the reciprocating container melts the adhesive inside the container, and a hopper for resupplying the container with adhesive is disposed in the rightmost position. Furthermore, a vacuum duct is provided in the container leftmost position, opposing the heating device, to provide vacuum filtration of evaporation derivatives generated when the adhesive is heated and melted. With a configuration of this sort an attempt has been made to scale-down the glue container, and at the same time to vacuum-filter constituents from evaporation in melting/liquefying the adhesive, to prevent the constituents from scattering about the apparatus interior.
As described above, in implementations in which a solid adhesive received within a container is heated and melted, and the liquefied adhesive is applied to a sheet sheaf, with additives such as viscosity promoters being included in such types of adhesive, they will include constituents that evaporate into the surrounding atmosphere when the adhesive is heated to a high temperature and melted. The evaporation derivatives have a propensity for splattering onto the apparatus interior or the apparatus exterior and clinging to surrounding objects, and when cooled to ordinary temperatures, solidifying and remaining as clung material.
To address this, as disclosed in above-cited Japanese Unexamined Pat. App. Pub. No. 2004-216769, the evaporation derivatives that issue from the glue container when the adhesive inside the container is heated and melted are vacuum-filtered, yet a problem arising therein is that in replenishing the container with adhesive, the evaporation derivatives cling to adhesive furnished in the hopper or other storage, or cling to the resupply path. The evaporation derivatives that issue from the container melt adhesive furnished within the hopper (adhesive prior to replenishment), or cling to the adhesive and form clots in it, leading to resupply-path clogging problems. Likewise, evaporation derivatives clinging to the resupply path also leads to the problem of the refilling adhesive getting stuck in and clogging the path.
To counter these problems, in the conventional structure in Pat. App. Pub. No. 2004-216769, a heating device is disposed to one (e.g., the leftmost) side of the reciprocating glue container, and the resupply hopper is disposed to the other (rightmost) side, opposing the heating device, but resupplying the container with solid adhesive in a situation in which adhesive therein has been melted at a high temperature leads to the problems just noted. Even supposing that the container is resupplied in a situation in which the adhesive within the container has been cooled to the extent that it will not evaporate, with the structure in this patent publication, the fact that after the container has been refilled with adhesive, it is shifted into the heating-device position on the opposite end of the container's reciprocation path, and there the adhesive is heated and melted, conceals a problem of requiring time until the replenishment adhesive within the container has melted and the apparatus is restarted.